The present invention relates to integrated circuits and, more particularly, to a voltage generator for use in a MOS integrated circuit.
As is known, during the manufacture of integrated circuits, some electrical quantities cannot be determined precisely at the design stage because they depend on manufacturing parameters which may vary randomly, although within statistically predictable limits. In other words, the same electrical quantity, for example, the gate-source voltage of a conducting MOS transistor, may have different values in different specimens of the same integrated circuit. This variability is a problem which becomes more serious with lower supply voltages of the integrated circuit. Since, in the design of integrated circuits, there is a tendency to reduce the dimensions of the transistors and consequently to reduce the supply voltage, the problem is experienced to an ever greater extent.
In integrated circuits, it is sometimes necessary to provide reference and/or biasing voltages which take account of this variability of the manufacturing process, that is, which are not a predetermined fraction of the supply voltage of the integrated circuit but which depend on the actual value of one or more electrical quantities dependent on the manufacturing parameters. According to the prior art, it is possible to produce current generators which are substantially independent of variations of the manufacturing parameters, but it is not possible to produce voltage generators having the same independence.
An object of the present invention is to provide voltage generators which are substantially independent of variations of the manufacturing parameters.
This and other objects and advantages are achieved by the generator including complementary MOS transistors interconnected in four circuit branches one of which contains a constant-current generator. Voltages picked up at various nodes of the circuit can be used as reference and/or biasing voltages of the integrated circuit, which account for the variability of the manufacturing parameters.